Electric brake apparatus



Oct. 15, 1935. JR

ELECTRIC BRAKE APPARATUS J. W. LOGAN` Filed Nov. 11, 1953 uIrl' INVENTOR JOHN VV. LOGAN,JR. BY

ATTORNEY Patented Oei. 15, 1935 UNITED STATES lPATENT OFFICE ELI-:cmo naAxE APPARATUS Application November 11, 1933, Serial No. 691,641

15 Claims.

This invention relates to electro-dynamic brake apparatus, and more particularly to electro-dynamic brake apparatus of the eddy current type adapted to produce diierent braking effects on dierent axles of a vehicle.

When a vehicle is decelerating the force of inertia exerted upon it causes the vehicle to tilt forward, the degree of tilting depending upon the degree of deceleration. Because of this tilting action a greater load is imposed on the front axles of the vehiclev during deceleration than upon the rear axles. As a consequence, the front wheels of the vehicle bear upon a track or roadway with greater force than do the rear wheels, and a greater braking eiort may therefore be exerted upon the iront wheels than upon the rear wheels without causing skidding. Since the brakes commonly employed on both rear and front wheels are the same, and since they are most generally applied with the same degree of braking force, it is obvious that with such an arrangement the maximum braking action cannot be. obtained on both front and rear Wheels, as the maximum degree of braking force must be limited to that which-will not cause the rear wheels to skid.

An object of my invention is to provide an electro-dynamic brake apparatus of the eddy current type in which the braking effect produced on each-axle of a vehicle is such as to correspond very nearly with the load on each axle during deceleration of the vehicle.

Another object is to provide a new type eddy current brake in which the desired braking characteristics are inherent within the brake and with which auxiliary or outside apparatus is not required, other than that normally used with an ordinary eddy current brake.

Still another object is tc provide an arrangement of eddy current brakes of the character referred to in which the braking eiiect on each vaxle of a vehicle corresponds very nearly with the load on each axle dLu'ing deceleration of the vehicle in either direction.

Other objects will appear from the following description, illustrated in the attached drawing, in which,

Fig. 1 is a schematic arrangement of one embodiment of my invention as applied to a railway vehicle.

Fig. 2 is an enlarged plan view showing an adaptation of eddy current brakes to the motor driven vehicle axles shown in Fig. 1.

Fig. 3 is a schematic representation o1' four of (Cl. 18S-2) my improved eddy current brakes associated with the four axles shown in Fig. 1.

Referring now to the drawing, the embodiment there illustrated comprises 'a plurality of eddy current brakes I0 associated with vehicle motors 5 I2 drivingly connected to axles I4 adapted to support a vehicle, the floor of which is diagrammatically indicated at I6.

Each eddy current brake I0 comprises a cuplike rotor or brake drum I8 within which is 10 mounted a stator 20. The stator 20 comprises a magnetic core member 22 having pole pieces 24 projecting toward and preferably coextensive with the axial length of the rotor TI3. Each core member is provided with an insulated'winding 26, 15 u which may have current supplied thereto in any suitable manner, such for example as by conductors 29 shown in Fig. 1, wherein the windings 26 of each pair of brakes are shown as connected in series, although other methods of connecting l0 may be used.

The pole pieces 24 of each brake are provided with faces adjacent the rotor I8 which relatively diverge from the inner adjacent surface of the rotor, so that tapered air gaps are formed between the pole pieces and the rotor, for a purpose which will hereinafter more fully appear.

The rotor IB of each brake is rigidly secured to the shaft of its associated motor I2, so that the rotor rotates at all times that the vehicle is in motion. A friction brake band 28, circumscribing the outer periphery of the rotor I8, is provided to produce a friction brake eiect on the rotor I8 to supplement the braking eiect of the eddy current brake when desired, as for exam- $5 ple at low speeds where the eddy current brake is relatively less effective. The brake band 28 may be actuated through levers 30 by any ci the commonly employed means.

An eddy current brake I0 is preferably associ- 40 ated with each axle I4 of a vehicle, and each brake preferably has air gaps between its stator and rotor tapered in the manner described but to a degree and in a direction such that the braking effect produced by each brake on its associated 5 axle corresponds closely with the relative load on that axle during deceleration of the vehicle. For example, considering the arrangement illustrated in Fig. 1, if the vehicle axles I4 there shown be designated from left to right by the letters A, B, 50 C and D, respectively, then the arrangement of air gaps in the brakes associated with these axles may be as indicated by the corresponding letters A', B', C' and D in Fig. 3, where it is assumed that the rotors I8 rotate in a counter-clockwise Il direction, as shown by the arrows, when thevehicle moves to the lett.

With reference to the arrangement shown in Fig. 3, it is to be understood that the air gaps in brakes A' and D have the same degree of taper, but taper in opposite directions. The air gaps in brakes B' and C also taper oppositely to each other and have the same degree of taper, but the degree ot taper is less than that o! the gaps in brakes A and D'. This difference in degree o1 taper is to be understood to be such that i! the distances across the gaps of the several brakes at the corresponding points indicated by the symbols da, da. do. and dn, corresponding to brakes A', B', C', and D', respectively, be compared, then dx is less than de, dn is less than de, and dc is less than dn, i. e. the gaps increase at this point progressiveiy from the left (one end of the vehicle) to the right (other end of the vehicle). If the distance between the other tip of each pole piece 24 and the associated rotor I8 be considered in a like manner the converse is true, i. e. the distance diminishes from left to right. The object and importance of this arrangement will appear subsequentiy.

In operation, when it is desired to brake a vehicle equipped with my improved eddy current brake apparatus, current is supplied to the windings 26 through the conductors 29 in a degree in accordance with the degree of braking desired. Each winding 28 therefore receives the same degree of energization. A magnetic flux will be produced in each brake having a path including the core member 22, the pole pieces 24, the rotor I8, and the air gaps between the pole pieces and the rotor, oi? that brake. This iiux will produce eddy currents in the rotor I8, which currents will in turn produce a counter flux partially opposing and partially adding to that produced by the stator in a manner such that the flux in the air gaps will be shifted in the direction of rotation of the rotor. If the direction of rotation be considered as counter-clockwise, as indicated in Fig. 3, then the ilux will be largely concentrated at the top left tip and the bottom right tip of the pole pieces 26. The eddy currents in the rotor of each brake will. therefore react with this concentrated or resultant ux to produce a retardingeiect on the vehicle.

As the vehicle begins to decelerate from motion to the left, the force of inertia will cause it to tilt, so that axle A carries more load than axle B, axle B carries more load than axle C, and axle C carries more load than axle D. The air gaps in the brakes associated with each of these axles are proportioned such that the braking eiiect on each axle is diierent, so as to correspond very nearly with the load on that axle for most rates of deceleration, and exactly with the load on each axle for one specific rate of deceleration, which is usually taken as that corresponding to the maxi mum rate of deceleration, i. e. brake A' produces a greater braking eiect on axle A than brake Br does on axle B, brake B produces a greater braking eiIect on axle B than brake C does on axle C, and so on. This is so because, as explained, at the point where the iiux concentrates the air gaps increase in size progressively from axle A toward axle D, and these progressive increases reduce, progressively, the total resultant flux in each brake available to produce a braking eiect, resulting in the diiierences in braking eiects already referred to. With such an arrangement, therefore, the brake on .each axle may be operated to produce its maximum braking eiiect, with the result that the vehicle can be brought to a stop more quickly than with the ordinary type oi brake as now used.

It' the direction of travel of the vehicle, and hence the direction oi rotation of the rotors IB,

be opposite to that assumed in the foregoing de- 5 scription, like results to those just described will be obtained, as the direction and degree oi taper of the air gaps for this direction oi rotation are such as to act in a like manner to that for the other direction of rotation. The flux produced by 1o the winding 26 is now shifted toward the top right and lower left pole tips of pole pieces 2l, i. e. in the direction of rotation oi the rotors I8. The distance across the air gaps of the several brakes at these points increases progressively from right 15 to left, i. e, just oppositely to that before described, but the air gap distances for the relative positions of the brakes for the two directions of travel correspond, i. e. the flux is concentrated across a gap in brake D corresponding to the gap 2o in brake A for the opposite direction oi travel, and so on for the other brakes. It will therefore be obvious that it is not necessary to make any changes in the brake apparatus when reversing the direction o! travel oi.' the vehicle, as the de- 2s sired characteristics for both directions oi travel are inherent within the brake apparatus.

While one illustrative embodiment of the invention has been described in detail, it is not my intention to limit its scope to thatl embodiment or soA otherwise than by the terms of the appended claims.

Having now described my invention, what I claim as new and desire to secure by Letters Pat ent, is:

l. In a vehicle brake apparatus, the combina tion with a plurality of axles adapted to support a vehicle producing different loads on said axles when the speed of said vehicle is varying, oi electro-dynamic brakes associated with said axles 40 and inherently operable. to produce a 'braking eifect on each axle corresponding closely with the load of each axle.

2. In a vehicle brake apparatus, the combination with a plurality of axles adapted to support 45 a vehicle producing different loads on said axles when the speed of said vehicle is varying, of elec tro-dynamic brakes associated with said axles, each of said brakes having a rotor and a stator defining a non-uniform air gap therebetween act- 50 ing to cause said brakes to produce a braking effect on each axle corresponding closely with the load on each axle while said brakes are in action.

3. In a vehicle brake apparatus, the combination with a front axle and a rear axle upon which 55 different loads are imposed when a vehicle supported by said axles ls decelerating, of electrodynarnic brakes associated with said axles, each of said brakes having a rotor and a stator c'ieiiningr an air gap therebetween, the gap in one of said 00 brakes being shaped to produce an efiect riierl`- ent from the gap in the other of said brakes, whereby the braking effect on said axles is diiferent.

4. In a vehicle brake apparatus, the comblna.- w tion with a front axle and a rear axle upon which different loads are imposed when a vehicle supported by said axles is decelerating, of electrodynamic brakes associated with said axles, each of said brakes having a rotor and a stator defining a tapered air gap therebetween, the gap or the brake associated with one axle tapering op positely to the gap of the brake associated with the other axle.

5. In a vehicle brake, the combination with a 1l front axle, a rear axle, and intermediate axles,

of electro-dynamic brakes associated with said of the brakes associated with the other of seid,

axles.

6. In a vehicle brake, the combination with a front axle, a rear axle, and intermediate axles,

of electro-dynamic brakes associated with said axles, each of said brakes having a rotor and a stator defining a tapered air gap therebetween,

the air gaps of the brakes associated with the intermediate axles being of less taper than that of the air gaps of the brakes associated with the other of said axles.

'7. In a vehicle brake apparatus, the combination with a pair of axles, of an eddy current brake associated with each of said axles, each of said brakes having a rotor and a stator with a taperedv air gap therebetween, the air gap in one brake being of less taper than the air gap in the other brake.

8. In a vehicle brake apparatus, the combination with a pair of axles, of an eddy current brake associated with each of said axles, each oi said brakes having a rotor and a stator with a tapered air gap therebetween, the air gap in one brake tapering in a direction opposite to that of the air gap in the other brake and each of said tapers being of a different degree.

9. In a vehicle brake apparatus, the combination of a pair of eddy current brakes adapted to brake a vehicle, each of said brakes having a rotor and a stator with anv air gap therebetween,

the stator being adapted to produce a magnetic flux across said gap to produce a braking effect, and means whereby the flux across said gap for equal energization of said brakes is relatively greater in one of said brakes for one direction of rotation and relatively less for an opposite direction oi rotation.

10. A vehicle braking apparatus comprising a plurality of eddy current brakes disposed in spaced relation longitudinally of a vehicle, each of said brakes having a rotor and a stator dening a tapered air gap therebetween, the taper of said gap progressively changing 'in said brakes along said vehicle.

11. In a vehiclebrake apparatus, the combination of a plurality of eddy current brake devices adapted 'to brake a vehicle, each of said brake de-l vices having a rotor and a stator deiininga tapered air gapl therebetween, the stator being adapted to produce a magnetic flux across said gap to produce a braking eiect on said rotor, the

air gap in each of said brake devices being dif- 5 ferent from the air gap in theother of said brake devicesand being effective in causing said brake device to produce a greater braking effect on its rotor when rotating in one direction than when vrotating in an opposite direction.

12. Vlin a vehicle brake apparatus, the combination with a plurality of vehicle axles upon which different loads are imposed when a vehicle supported by said axles is decelerating, of a plurality of electrodynamic brake devices associated with said axles, each of said brake devices having a rotor and a stator defining a. tapered air gap therebetween, the air gaps in the brake devices associated with the axles adjacent the iront end of the vehicle tapering in an opposite direction to the air gaps of the brake devices associated with the axles adjacent the rear end of the vehicle. y

13. In a vehicle brake apparatus, the combination of a plurality of eddy current brake devices adapted'to brake a vehicle, each oi said brake 25 devices having a rotor and a stator defining a tapered air gap therebetween, the stator being adapted to produce a magnetic ilux across said gap to produce a braking effect on said rotor, the gap in each of said brake devices being different from that in the other brake devices either as to direction of taper or as to degree of taper.

14. A vehicle braking apparatus comprising a plurality of eddy current brake devices adapted to be disposed in spaced relation longitudinally of a vehicle, each of said brake devices having a rotor and a stator defining a tapered air gap therebetween, the taper of said gaps progressively changing in said brake devices along said vehicle irom a taper in one direction to a taper in an opposite direction.

15. In` a vehicle brake system, the combination with a plurality of vehicle axles, and a plurality of driving motors associated with said axles, each of said motors having a shaft, of a plurality of eddy current brake devices operatively connected to said shaft, each of said brake devices having a rotor and stator defining a tapered air gap therebetween, the taper of each gap in each brake device being diierent, whereby for equal energization of all of the brake devices a different braking eiect is produced on each axle.

JOHN W. LOGAN, Jn. 

